Misuse of "\n", "\l", and "\p" in a script.
Seriously, only use "\n" and then a "\l" if necessary in-between "\p"s. If you take a good look at the scripts in the original games, they never go any farther than that. I'm sick of seeing people use multiple "\l"s in a row, or even (god forbid) several "\n"s in succession. It looks incredibly unprofessional and it causes my enjoyment of playing a hack suffer as it becomes boring to scroll through these long textboxes. Because of the unlimited space for text provided by this error, you are more tempted to create run-on sentences if you can type for as long as you want. But if you are limited to a certain space, you have to choose your words wisely (like a haiku), making the game more aesthetically and linguistically appealing.